Thank you again Danco. I'm going to follow your lead with the block an buffer. Probably worth having on hand regardless.
My bud just shot his BCA 16" upper with a PSA lower and a Spikes lower. Both with cheap LPKs. His cycles functions and feeds perfectly. With both lowers if he installs a "heavy spring" in the buffer tube it wont pick up the next round and becomes a single shot. He is using ASC .450 mags.
BCA probably designs their uppers to work with cheap/stock stuff. Would make sense and probably 90% of their buyers arent gunsmiths nor probably care. KISS!